A production line for semiconductor substrates and membrane substrates inspects defects on surfaces of the semiconductor substrates and membrane substrates in order to ensure and improve product yields. Conventional technologies are disclosed in Japanese Patent Application Laid-Open Publication No. 9-304289 (patent literature 1) and Japanese Patent Application Laid-Open Publication No. 2000-162141 (patent literature 2). In order to detect tiny defects, these technologies condense a laser beam into several micrometers, irradiate the laser beam onto a sample surface, collect and detect scattering light from defects, and detect a defect whose size ranges from nanometers to several micrometers or more.
As semiconductor devices are miniaturized, the required defect detection sensitivity increases accordingly. There have been used sensitivity improvement techniques such as polarization detection of scattering light (patent literature 3). The polarization detection can selectively suppress scattering light (hereafter referred to as roughness scattering light) resulting from sample to surface roughness of a laser irradiation portion and improve the detection sensitivity.
In recent years, there is an increasing need to monitor sample surface roughness states other than the defect detection sensitivity. The sample surface roughness is calculated based on the roughness scattering light intensity and is referred to as a haze signal. The haze signal is monitored for process management (non-patent literature 1).